docs: refresh the roadmap, trim the cross-platform guide, and update the Linux setup and desktop guides

[y3owk1n]

Description

This PR refreshes the four platform docs that had drifted from the tree. The roadmap still listed Windows work that shipped in the last release (full UIA tree walk, monitor_select) and "make unsupported capabilities fail loudly" as open. It now records that Linux and Windows parity is complete, that the near-term work is proving both in use under the six-clean-releases rule, and points at the open enhancement issues and the COSMIC and GNOME state rather than a stale feature list.

The cross-platform guide loses about a fifth of its length. Footnotes that had grown into essays are cut back to the facts they own, repeated ADR justifications are dropped, the footnote numbered 7 twice is renumbered, and the accessibility file table names files that exist. Every heading that other docs, skills and code comments link to is kept, and the generated platform-support table is byte-identical.

The Linux setup and desktop guides now describe the lifetime keyboard proxy from #1600 consistently, list Wayfire and the wayland-other refusal in the backend tables, quote the daemon's real error strings under troubleshooting, and name wayland-info instead of the nonexistent wl-info.

Related Issues

None.

Target Platform

• Platform-agnostic (shared logic, no OS-specific code)
• macOS
• Linux
• Windows

Type of Change

• feat — New feature
• fix — Bug fix
• refactor — Code restructuring (no behavior change)
• perf — Performance improvement
• docs — Documentation only
• test — Adding or updating tests
• chore — Build, CI, dependencies, tooling

Cross-Platform Checklist

• OS-specific files use correct build tags (e.g., //go:build darwin) — N/A, docs only
• No darwin imports from untagged (shared) code — The One Rule — N/A, docs only
• Stub implementations added for other platforms (returning CodeNotSupported) — N/A, docs only
• N/A — This PR does not touch platform-specific code

General Checklist

• Code formatted (just fmt)
• just ci passes — N/A, docs-only fast path: just fmt-check && just lint exit 0, plus go test ./internal/architecture/ for the doc-link, guide-citation and platform-support guardrails
• Tests added/updated for new or changed functionality — N/A, docs only
• Documentation updated (if applicable)
• PR title is a conventional commit
  subject written for users — this PR squash-merges, so the title is what
  Release Please ships in the changelog, not the commits on the branch

Additional Context

Every quoted log and error string in the two Linux guides was grepped against the tree, and every anchor into the four files from the rest of the repo was checked against the new headings. Two neighbouring docs still carry the same drift and are left for a follow-up: the README platform table shows Windows without Vision OCR or monitor_select, and docs/CONFIGURATION.md says the vision strategy is unavailable on Windows.

[greptile-apps]

Greptile Summary

Refreshes the platform documentation to match current Linux and Windows support.

• Corrects the KDE scroll fallback description to distinguish its libei portal path from the wlroots virtual-pointer path.
• Documents Wayfire and unsupported wayland-other sessions consistently.
• Updates Linux setup, troubleshooting commands, desktop guidance, and roadmap priorities.
• Condenses the cross-platform guide while retaining its capability and contributor references.

Confidence Score: 5/5

The documentation-only PR appears safe to merge with no outstanding actionable findings.

The previously reported KDE fallback problem is fully fixed by distinguishing wlroots virtual-pointer fallback from KDE's libei portal fallback, and the additional KDE uinput descriptions agree with the current routing behavior.

Important Files Changed

Filename	Overview
docs/CROSS_PLATFORM.md	Condenses the cross-platform reference and accurately clarifies KDE's uinput and libei scroll paths.
docs/LINUX_SETUP.md	Updates backend, permission, setup, and troubleshooting guidance, including a complete fix for the prior KDE fallback wording.
docs/LINUX_DESKTOPS.md	Refreshes KDE, wlroots, Wayfire, hotkey, and unsupported-compositor guidance.
docs/ROADMAP.md	Replaces completed parity work with current reliability priorities and prospective platform directions.

_{Reviews (2): Last reviewed commit: "docs(linux): name libei as the KDE scrol..." | Re-trigger Greptile}